1. Field of the Invention
The invention relates to a layout structure for a liquid crystal display, and more particularly to a layout structure for a liquid crystal display capable of having fewer data lines.
2. Description of the Related Art
Recently, small-sized TFT (Thin Film Transistor) LCD (Liquid Crystal Display) modules have been widely used in small hand-held electronic devices, such as PDAs (Personal Digital Assistants), and mobile phones. FIG. 1 is a schematic illustration showing a conventional TFT-LCD module, where the TFT-LCD module includes sub-pixels p arranged in an m×n array, a source driver unit, and a gate driver unit. The source driver unit provides n data channels connected to data lines S1 to Sm respectively. The gate driver unit provides m scan channels connected to the scan lines G1 to Gn respectively. Every three sub-pixels p constitutes a pixel, and represents the colors red, green and blue respectively. Each sub-pixel p is coupled to a corresponding data line through a transistor T. The gate of the transistor T is coupled to a corresponding scan line. A typical source driver IC has 384 channels and may provide the channels required for 128 pixels, and a typical small-sized TFT-LCD only needs one source driver IC.
Requirements for frame quality and frame resolution are steadily increasing, the number of channels of the driver IC used in this application must be increase as well. The number of source driver channels must be increased because for each pixel there are three channels for red, green, and blue sub-pixels that have to be added. A TFT-LCD with a resolution of 176×220 may require 528 (176×3) channels in the source driver IC. Therefore, a source driver IC having 384 channels provides an insufficient number of channels, as required by the LCD. The chip size of the driver IC of the source driver unit is mainly limited by pin number (pad-limited), while the chip size of the driver IC of the gate driver unit is mainly limited by the internal circuit size (core-limited). Increasing the channel number may invariably increase the pin number of the driver IC of the source driver unit, thereby greatly influencing chip size.
There are several methods of using a TFT-LCD with high resolution.
1. It is possible to use two general source driver ICs each having 384 channels. However, the cost of the driver ICs is increased. In addition, because the small-sized TFT-LCD module is mainly used in small devices, the size of the mechanism has to be increased if two ICs are needed, which doesn't meet the requirement of having a small device size. Furthermore, it is possible that only a small portion of the channels of the second source driver IC are used. In this example, only 144 (528−384) channels of the second IC are used, which is not economically efficient.
2. It is possible to provide all the channels required by a driver IC. However, this may increase packaging difficulties, and the number of channels increased is also limited. Additionally, verifying the redesigned IC is a time consuming process.
3. It is possible to enlarge the size of the driver IC in order to increase the number of channels. However, the cost and mechanism volume may be increased, which may not meet size requirements for small devices. Additionally, verifying the redesigned IC is a time consuming process.